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Proposed Conceptual Framework
This article discusses a proposed conceptual framework that has proven useful in the study of consciousness. Definition of "Consciousness" "Consciousness" is the set of all possible conscious experiences. This definition is similar to notions of "space" as the set of all possible locations and of "time" as the set of all possible moments. In other words, under this definition, "consciousness" is a fundamental contextual feature. Possible antecedents of the above definition include: --Certain ideas of eminent western consciousness researchers and philosophers, e.g. Christof Koch and David Chalmers; and --Eastern views that all conscious experiences exist. The above definition can be contrasted, on the other hand, with proposals that consciousness is a process or system or that consciousness is produced by a brain. Under the above definition, consciousness is fundamental, while those proposals imply that consciousness is somehow composed of or dependent on other things. For greater logical robustness, context can be explicitly added to the above definition. For example, one could define "consciousness" for a given context as the set of all experiences that are possible in that context. With this addition, two instances of consciousness would only be inconsistent if both were for the same context and the two were different from each other. One way to evaluate the above definition is to use it and discover consequences of doing so. Indeed, Jim Beran was led to adopt it by a desire to avoid the so-called "hard problem"; the hard problem is sometimes expressed as a question, e.g.: How can a brain produce consciousness? Under the above definition, on the other hand, consciousness is not produced by the brain or by anything else, but rather is a fundamental feature of a context. The above definition also beneficially allows new descriptions of relationships between brains and consciousness. Some new ways of describing such relationships posit that consciousness includes a subset of experiences that are combinations of other, simpler experiences between which transitions occur. (One might also posit another subset of experiences that are combinations of other, simpler experiences between which transitions do not occur.) With this addition, one can then consider descriptions in which, for example, brain operations cause transitions or changes between conscious experiences. Neural-to-Conscious (N-to-C) Transduction The verb "to transduce" often refers to converting something from one form to another; a familiar example is converting energy from one form to another. Merriam-webster.com provides the following example: "essentially sense organs transduce physical energy into a nervous signal". We therefore use the expressions "neural-to-conscious transduction" and "N-to-C transduction" to describe an operation that responds to neural signals by making transitions or changes between conscious experiences. In other words, an N-to-C transduction operation transduces from neural signals to transitions or changes in conscious experience. The proposed conceptual framework also assumes that a conscious brain includes one or more components that perform N-to-C transduction. This assumption is consistent with empirical evidence that neural signals within one's brain, e.g. neural signals received from sense organs, cause change in one's conscious experience. Definition of "Neural Circuit" A leading neuroscience textbook states: "Neurons never function in isolation; they are organized into ensembles called neural circuits that process specific kinds of information and provide the foundation of sensation, perception, and behavior." (Purves, D., Augustine, G.J., Fitzpatrick, D., Hall, W.C., LaMantia, A.-S., McNamara, J.O., and White, L.E., Eds., Neuroscience, Fourth Edition, Sunderland, MA: Sinauer Associates, 2008, p. 11. For other examples of how the term "neural circuit" is used, see the page titled Usage Examples of "Neural Circuit" and Related Terms.) From this explanation and other considerations, we have arrived at the following definition of "neural circuit": A multi-cell configuration in which signal transfer occurs between neurons and in which cells in the circuit collectively operate in a way that depends on the signals transferred between neurons. Note the following features of this definition: --The term "multi-cell configuration" allows the possibility that a neural circuit could include other types of cells in addition to neurons, e.g. glial cells; --The broad term "signal transfer" includes, for example, transfer of signals across synapses, through gap junctions, or through other mechanisms, possibly mechanisms not yet discovered; --The expression "cells in the circuit collectively operate" is intended to encompass not only operations in which cells are concurrently active, but also operations in which cells operate alternately, in sequence, and so forth; and --The requirement that cells operate collectively "in a way that depends on the signals transferred between neurons" means that collective operation must be tied to signal transfer. Many types of operations could satisfy this requirement, e.g. information extraction from transferred signals; modification of information in transferred signals; transmission or storage of transferred signals; etc. "N-to-C Transducer Circuits" Using the above definitions, we posit the existence in a conscious brain of neural circuits that perform N-to-C transduction. We sometimes refer to such circuits as "N-to-C transducer circuits" or, more simply, "N-to-C transducers". It follows from the above definition of "neural circuit" that each N-to-C transducer in a conscious brain includes multiple cells. This is consistent with empirical evidence from brain imaging studies showing multiple active regions in brain activity patterns that correlate with various types of conscious experience.